Produced by journalist Maria Awes, the three-part documentary also features former FBI agent John Douglas and biographer Gary Garrett.

It was like a terrifying nightmare come to life: On November 3, 2016, 30-year-old Kala Brown was found trapped on a South Carolina man's property, chained to the wall inside a shipping container. Her boyfriend, Charles Carver, had been shot and killed on the property some months earlier.

Kala's captor, Todd Kohlhepp, was a 45-year-old real estate agent at the time. He had a criminal history, sure, but he was also a successful local businessman and possessed an IQ of 118. It's this chilling duality that makes Todd Kohlhepp's crimes feel so eerie and unexpected — and what makes him a fitting subject for the ID channel's new documentary miniseries, Serial Killer: Devil Unchained, which airs on Mondays at 9 p.m. ET.

Produced by investigative journalist Maria Awes, the three-part documentary delves deeper into Todd's early life and crimes with the help of Todd's former colleague (and now biographer) Gary Garrett and former FBI agent John Douglas (who's best known for being one of the first-ever criminal profilers and inspiring Netflix's hit crime show Mindhunter).

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Photo credit: Investigation Discovery

"Todd Kohlhepp is really intelligent ... he's very, very introspective," John tells GoodHousekeeping.com. "He agreed to take on and fill out our [criminal profiling interview] form, and when he filled out the form for us, he answered way beyond anything I'd ever experienced. He actually added pages, additional sheets of paper, where he wanted to fully describe the cases and his motivation. He wanted to learn why — what made him be this type of killer."

In Devil Unchained, Maria, Gary, and John aim to uncover more about just that: what dark secrets made Todd the murderer he became. Before you watch, here's a look at everything we know about the serial killer (and his horrific crimes) so far.

Todd Kohlhepp's early life

Todd Kohlhepp (then named Todd Christopher Sampsell) was born on March 7, 1971 in Fort Lauderdale, Florida. He was just a toddler when his parents divorced, and he spent his early childhood living with his mother and stepfather in Georgia and South Carolina. By the time he was 12, however, it was decided he should live with his dad — so he packed his bags and moved across the country to Arizona.

According to various court documents, Todd's horrific crime was not totally out of line for the teenager: He had exhibited violent behavior from a very young age (including attacking other children and poisoning pet fish with bleach), and a neighbor in Arizona described him as a "devil on a chain." But looking at everything John has learned about Todd's past, it makes a lot of sense.

"You could see where he was coming from as a child: He was abused, abandoned, his grandfather hit him with a cattle prod," John says. "Even in elementary school, he was a bully. By the time he was 9, he ended up in a mental hospital. He was very, very angry and combative. He really became the product of this very dysfunctional family."

Ultimately, the judge in Todd's case found him to be "very bright" but also "emotionally dangerous," and Todd was sentenced to 15 years in an adult — not juvenile — prison.

Moving back to South Carolina

Todd went on to serve 14 years in prison before being released in 2001, when he was required to register as a sex offender. The label was one he took with him from Arizona back to South Carolina, where he returned shortly after his release.

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At this point, though, Todd's life seemed to be on an upward track: He went to school and ultimately earned two bachelor's degrees (one in computer science and one in business) before becoming a real estate agent. Little did those around him know the dark secrets he was hiding.

Getting caught

On November 3, 2016, Spartanburg County police conducted an investigation of Todd's property after discovering that a ping from two missing persons' cell phones placed them in the area. It was during this search that they heard banging inside a metal shipping container on the property, in which they discovered 30-year-old Kala Brown chained to the wall.

Eventually, with Todd's cooperation, police found two other bodies buried on the property, which belonged to 29-year-old Johnny Coxie and 26-year-old Meagan McCraw-Coxie, a couple who had been missing since December 2015. Todd confessed to murdering the husband and wife, as well as the victims in the long-cold 2003 Superbike case, in which four Chesnee, South Carolina motorcycle shop employees were mysteriously shot and killed. In total, he was charged with seven counts of murder, plus multiple counts of kidnapping and weapons charges.

Where Todd Kohlhepp is today

Ultimately, Todd was given seven consecutive life sentences for his crimes, and he's currently serving out these sentences at Broad River Correctional Facility in Columbia, South Carolina. But when it comes to this serial killer, there are still some unknowns: For example, Todd has claimed he murdered at least two other victims whose bodies have not yet been found ... but is he to be believed?

This is one of the questions that producer Maria set out to answer with Devil Unchained. And through exclusive access to Todd — and John's 57-page protocol for criminal profiling interviews — they might have come close.

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Photo credit: Investigation Discovery

"I believe when he says he killed two other people in South Carolina," John says. "He was so specific about how he went about killing them and how he cleaned up the area ... I have this expression: 'To understand the artist, you must look at the artwork.' Behavior reflects personality. He was just so consistent and specific."

Overall, though, John says Todd is different than any other serial killer he's ever encountered in his career. For one, he's a mass murder-turned-serial killer, and the only other similar criminal he's interviewed was Dennis Rader, the so-called "BTK Killer." But even then, he says, the BTK Killer's crimes had a sexual component ... and Todd's were something else entirely.

"He was more of a retaliatory type of person," John says. "If he felt you were doing him wrong, he would get even. He's very patient — he would wait months — but he's going to come back. He's going to get you. He was a different breed of cat."

To learn more about Todd Kohlhepp and the truth behind his crimes, tune into Investigation Discovery's documentary miniseries Serial Killer: Devil Unchained on Mondays at 9/8 c.

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